Phase inverter



July 18,V 1944. A. KECKETAL E 2,353,672

' PHASE INVERTER Filed July 28. 1942 A T TORNE Y Patented July 18, 1944 Brumbaugh, Lansdowne, Pa., assignors to Radio Corporation of America, a corporation of Del-A aware Application July 2s, 1942, serial No. 452,608

` 4 claims. (ci. 172-238) This application concerns a new and improved voltage or potential phase inverter by` means of which voltages or potentials of opposed phase but which are otherwise substantially identical may be derived from single phase voltages or other potentials. The novel means of this application is of general application in the radio and associated arts. A particular use therefor is in the frequency modulated wave analyzer of John M. Brumbaughs U. S. application Serial #447,629, filed June 19, 1942. A

In describing our invention a phase inverter arrangement as disclosed in the said application will be used, and this phase inverterhas been illustrated in the single ligure of the drawing.

Referring to the gure of the drawing, a voltage or potential, the phase of which' is to be inverted or reversed, is supplied at the connectors marked AC Input and appears across a resistance R56, which is connected-by a condenser C45 to ground. The potential here may represent, for example, the modulations derived by demodulating a wave length modulated wave yor other potentials of this general nature. The resistance R58 may be any input resistance and may, for example, also be the output resistance of a preceding' stage as in said application. The potential is applied by coupling condenser C46 to the control grid |60 of the tube V|0. Control grid |60 is coupled to its cathode |64 by a resistance R60 and a self-biasing degenerative resistance R62, which also is an output resistance or load. The control grid |60 is also connected by a relatively high resistance R6| to the positive terminal of a source of potential, the negative terminal of which is connected to the groundA end of R62. The anode |10 of tube V|0 is connected by a resistance R63 to the positive terminal of the source, this resistance R63 serving as a load or output resistor for the tube. The potential drop between the anode end of resistor R63 and ground is supplied by coupling condensers C49 and C50 to two output connections, A and A'. 'I'hese output connections also include lter resistors R66 and R69. The resistor R62 is also coupled by ycondensers C48 and C5| Vto the two output terminals labeled B and B'.

and the voltage drop across R62, due to the quiescent plate current iiowng through R62, obtains the correct operating control-grid potential for` the tube VID. R62 and R63 together compose the total load resistance of the tube V| 0.

Since the cathode and plate are of opposite alternating potential with respect to ground, these points are used to obtain the output voltages or potentials which are`l alike except for phase.

Theoretically R62 and R63 should be equal, but because of unequal shunting eiects of the external circuit, R63 is made slightly lower in resistance value than R62. This makes the alternating voltage from plate |10 to ground equalto that from cathode |64 to ground.

Capacitors C48 and C49 are coupling capacitors to two output connections, such as, for exlample, connections to the diode in the meter circuit of the said above identied application;

while R61 and R68 are ground return resistors. Similarly, C50 and C5| are coupling capacitors Afor two other output connections, such as, for

example, connections to the asher circuit and R69 and R10 are the grid resistors for the asher input circuit of the said above identified application The applied voltage or potential is reversed in` phase by thetube action so that the voltage or,I

potential on the anode |10 is reversed with respect to the voltage or potential to the grid |60. The voltage in R62, however, is in phase with the applied grid voltage. Thus, if we take the output from the anode resistor R63, we will have a potential corresponding to the applied potential but of opposed phase. This potential appears at the points marked A and A'. If we take the output from the cathode resistor, R62, We have a potential identical to the potential derived from R63, but of the same phase asv the potential or voltage impressed on grid |60. This latter potential appears at the connectors marked R56 is the plate load resistor of the preceding stage. The voltage from this stage is coupled to the phase inverter through capacitor 4C46.

`.C46 and R50 comprise a decoupling filter. The

control grid biasing potential is supplied by the voltage divider composed of the resistances R66.

and RBI. 'I'his biasing voltage is positive with respect to ground. The sum of this potential B and B.

In this reverser arrangement, as shown, the full cathode bias resistor R62 drop is supplied to the control grid '|60. This provides a negative bias thereon which may be too high and then to compensate this high negative potential,

some positive potential is supplied to the control gridV by resistor RII. Thus, the voltages or potentials of reversed phase are obtained from balanced resistors R62 andv R63 in the plate and cathode of the same tubeand the potentials or voltages must be identically equal in magnitude since they are produced by the same current owing in substantially matched resistors. Note that the resistors R62 and R63 may not be exactly equal because of reasons pointed out here-l inbefore. Thus, the voltage path in our system is independentI of tube gain. In arrangements known heretofore, the bias has been arranged by means of a tap on the cathode resistor, and

this gives full cathode degeneration only if the grid is driven from an impedance which is quite low compared to the grid resistor. The bleeder bias method of the present invention gives full degeneration with a high impedance source. It also tends to maintain a more stable operating point on the tube characteristic. As is well known, many phase inverters of the prior art use two tubes and, as a consequence, are subject to changes of current due to changes in the two tube characteristics. requirement is that the impressed voltages give phase reversed voltages identically equal in magnitude and the arrangement shown meets this requirement.

When the phase inverter of our invention` is used in a monitor of the nature described in the above identiiied application, the points A and B may be connected byswitch S3 to a asher circuit; while the points A and B' may be connected by a switch S4 to a meter circuit.

In other uses one output connection to each of the output impedances only is used.

In an arrangement which operated satisfactorily to handle potentials fmodulation frequency the tube VIO was a-6J 5, and the circuit elements -were as follows:

1. In apparatus for producing two substan- Here a fundamental tical but phase opposed potentials appears in said impedance connected to the electron receiving electrode and the other of said two substantially identical but phase opposed potentials appears in the impedance connected to the cathode of Y said tube.

nected between the electron receiving electrodey and ground, a connection for impressing the po tential drop in the impedance connected between the cathode and ground on the control electrode of said device, a connection for impressing an opposing direct current potential from said tially identical phase opposed potentials which correspondto a first potential, a tube having an electron receiving electrode, a control electrode and 'a cathode,.connctions for impressing said rst potential on said control electrode and cathode, a source of direct current, two output impedances one connected to the cathode and one connected to the electron receiving electrode, a connection for impressing the potential drop in the impedance connected'to the cathode on the control electrode, and a connection for impressing an opposing potential from said source of direct current on the control electrode ofA said tube, whereby one of said twc substantially idensource of direct current on the control electrode of said tube, and means for impressing said first potential on the control' grid andcathode of said device whereby one of saidl two substantially identical but phase opposed potentials appears in said impedance connected between the electron receiving electrode and ground and the other of said two substantially identical but phase opposed potentials appears in the impedance connected between the cathode of said tube and ground..

3. In a system for deriving from alternating current of a given phase, substantially equal alternating currents of opposed phase, an electron discharge device having a control grid,.an anode, and a cathode, connections for impressing said 1alternating current on the control grid and cathode of said device, a source of direct current potential, a resistive potentiometer connected across said source of direct current potential, said potentiometer including a resistance between the control grid and positive terminal of said source and a resistance between the control grid and negative terminal of said source, an output impedance connected to the anode of said device, and an output impedance connected between the cathode of said device and the negative terminal of said source.

4. In a I potential reverser an electron discharge device having a control grid. an anode, and a cathode, a source of direct current potential, an output impedance connected between the cathode of said device and the negative terminal of said source, a connection between the grid of said device and the terminal of said output impedance remote from said cathode, connections for impressing said potential between the control grid of said device and ground, and the said terminal of said resistance, an impedance connecting the anode of the device to the positive terminal of said source, an'output impedance connected to the anode of said-device, an output circuit connected to said last named impedance,

and an output'circuit connected to the impedance connecting the cathode of said device to the negative terminal of said source.

ALFRED Knox.

JOHN M. BRUBBAUGH. 

